Front printer

ABSTRACT

A printer in which selectively activated hammers drive selected print slugs against a document by striking interposers which are maintained in contact and associated with the selected slugs and which transmit the force of the hammers to the slugs. Each slug is associated with a particular interposer and both are mounted in a continuous chain which moves across the document at the print line and is located on the same side of the document as are the hammers. The interposers are resiliently mounted in the chain and the slugs are biased away from the document and maintained in contact with the interposers. Preferably, each slug is partially located in an open-ended bore within its associated interposer and has a flanged end on which a type character is located projecting out of the bore. The slug&#39;&#39;s flange is maintained in contact with the open end of the interposer and the centroids of the slug and interposer are aligned perpendicular to the document and along the center of the bore. Thus, an impact force on the interposer is transmitted to the flange of the slug to drive the slug toward, and perpendicular to the document.

United States Patent [72] Inventors Frederick E. Carroll Lynnfield; James [-1. Edwards, Winchester; Lynn W. Marsh, Jr., Melrose, all of Mass. [21 l Appl. No. 853,752 [22] Filed Aug. 28, 1969 [45] Patented Oct. 12, 1971 [73 Assignec Mohawk Data Sciences Corporation Herkimer, N.Y.

[54] FRONT PRINTER 11 Claims, 3 Drawing Figs.

[52] US. Cl 101/93 [51] Int. Cl B4lj [50] Field of Search... 101/93 [56] References Cited UNITED STATES PATENTS 2,893,313 7/1959 Pekar et al 101/93 C 2,897,752 8/1959 Maimros et al. 101/93 C 3,399,619 9/1968 Sims 101/93 C Primary Examiner-Robert Peshock Attorneys-Francis J. Thomas, Richard H. Smith, Thomas C. Siekman and Sughrue, Rothwell, Mion, Zinn and MacPeak ABSTRACT: A printer in which selectively activated hammers drive selected print slugs against a document by striking interposers which are maintained in contact and associated with the selected slugs and which transmit the force of the hammers to the slugs. Each slug is associated with a particular interposer and both are mounted in a continuous chain which moves across the document at the print line and is located on the same side of the document as are the hammers. The interposers are resiliently mounted in the chain and the slugs are biased away from the document and maintained in contact with the interposers. Preferably, each slug is partially located in an open-ended bore within its associated interposer and has a flanged end on which a type character is located projecting out of the bore. The slugs flange is maintained in contact with the open end of the interposer and the centroids of the slug and interposer are aligned perpendicular to the document and along the center of the bore. Thus, an impact force on the interposer is transmitted to the flange of the slug to drive the slug toward, and perpendicular to the document.

PATE N TED um 1 21971 SHEET 1 OF 3 FIG. I

INVENTORS FREDERICK ECARROLL JAMES H. EDWARDS LYNN W. MARSH JR.

ATTORNEY FRONT PRINTER BACKGROUND OF THE INVENTION This invention relates to high-speed printers and, more particularly, to those printers which are commonly called front printers," i.e., printers in which the entire printing mechanism is located on one side of the document being printed upon.

- Numerous printers have been developed to print the output information of data processing apparatus. Generally, in these high-speed printers, a plurality of print hammers are arranged along the line at which characters are to be printed (i.e., the print line) and selectively strike an inked ribbon and document to force them against type characters on drum or continuous chain revolving at high speed on the other side of the document. The document being printed upon is generally a paper sandwich" made up of alternating sheets of paper and carbon with the top and bottom sheets being paper. The ribbon provides the ink for the topmost sheet of paper.

Certain drawbacks are inherent in such a printer. The print hammers must provide a large amount of energy to force the ribbon and paper sandwich against the type characters on the drum or chain. Another problem is side ghostingunwanted impressions made by those characters located on the drum or chain adjacent to the characters being printed; due to its thickness, the paper sandwich cannot be forced against the drum or chain at only one particular point.

These drawbacks are avoided by utilizing a front printer in which the print hammers drive print slugs on which type characters are located against the document, rather than force the document against the type characters. With front printers, a drum or chain is not required in back of the document. The entire printing mechanism is located in front of the document and only an anvil is needed in back. This allows the printer to be easily moved to print on oversized document or documents which are held in fixed positions. With each individual type character being independently driven against the paper sandwich, side ghosting" is eliminated. Also, the print hammers need not be designed to provide the large amount of energy necessary to force the ribbon and paper sandwich against a type character; they need only drive the print slugs against the ribbon and document.

However, for satisfactory print registration on the document, the print slugs must travel in a true path perpendicular to the document. To meet this requirement with hammers which directly strike the slugs, the hammers must impact the slugs in a direction perpendicular to the document. In addition, they must strike the slugs squarely and in line with the centers of the slugs. Deviation from these conditions causes wear and vibration problems as well as poor print registration.

However, some printers utilize hammers which move along short arcs and not in directions perpendicular to the document. Because of manufacturing tolerances, the impacting surfaces of the hammers and impacted surfaces of the slugs are never exactly flat to allow the hammers to squarely strike the slugs. For the hammers to impact the slugs in line with their centers, precise timing in activating the hammers is required.

SUMMARY OF THE INVENTION It is the primary object of this invention to provide a front high-speed printer having print slugs which are driven in a true perpendicular path toward the document.

This object and others are achieved by a printer in which selected print slugs are driven toward the document by selectively activated hammers which strike interposers located between the hammers and selected slugs. Part of the force of each hammer upon an interposer is transferred to a selected slug to drive it toward the document.

Since each slug's direction of movement depends almost solely on its relationship with an interposer, the directions in which the hammers move when activated are not limiting. Similarly, the timing of hammer activation is not critical as long as sufficient portions of the hammers strike the interposes to impart forces on the selected slugs toward the document. Also, the hammers need not strike squarely as is necessary when the slugs are struck directly.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a schematic perspective view of a preferred embodiment of the printer.

FIG. 2 is a view, partly in section, showing the hammers and the print chain in which the print slugs and interposers are mounted.

FIG. 3 is a view showing one of the hammers and a section through the print chain.

DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 shows a front printer printing upon a document comprising a paper sandwich l which is moved an increment in the direction shown after each line is printed. The document I has edge perforations la which are engaged by a suitable means for moving the document, such as sprocket teeth 2a on a rotatable drum 2.

Printing is accomplished by driving print slugs, which are mounted within a continuous print chain 3 (schematically illustrated), against the document. The drum 2 also provides the anvil surface necessary to resist the forces of the print slugs on the document.

The entire printing mechanism is located on one side of the document and mounted on a base 4. The print chain 3 revolves around driving and idler pulleys, 5a and 5b. The driving pulley ra is connected to the shaft 6a of a motor 6. The print chain revolves in a plane substantially parallel to the document at the print line. It moves across the document at the print line between upper and lower guide members, 7 and 8. The guide membersare located in the same plane as the chain and thus assure vertical registration of the print characters on the document. At the print line, a plurality of print hammers 9 are provided to drive selected slugs mounted in the print chain against the document.

Each print slug has mounted thereon an individual type character. The type characters make up one or more fonts. The print chain moves at a constant speed in a fixed continuous path and a conventional code disc 10 is mounted on the motors shaft 60. It contains a plurality of slots which represent the moving type characters and also an additional slot for indicating the end of each font. Light from a light source 11 is directed onto the code disc and passes through the slots therein and onto a photosensitive unit 12. By this well-known arrangement, the photosensing unit produces electrical outputs representing the positions of the type characters on the slugs within the moving print chain 3. Such electrical signals are then used to properly time the activation of the hammers 9.

An inked ribbon 13 is located between the document 1 and the print chain 3 at the print line. The ribbon is fed from a supply spool a to a takeup spool 14b. When a print slug is driven toward the paper sandwich, the print ribbon is forced against the topmost sheet to form an impression thereon.

In FIG. 2, the print chain is shown interposed between the hammers 9 and the ribbon l3, document 1 and drum 2. As illustrated, the print chain 3 comprises a plurality of separable slug carriers 15, one of which is shown in section. Each carrier 15 has mounted therein two print slugs 16. Each print slug is made up of a straight portion 16a having a flange 16b at one of its ends. The type character 17 associated with each slug is mounted on the flanged end. Also mounted within each slug carrier is a pair of interposers 18, each of which is associated with one of the slugs l6 and located between that slug and the hammers. Each interposer is mounted in the carrier with a resilient bushinglike member 19. The interposers each contain an open ended bore 18a within which is tightly fitted the straight portion 16a of a print slug. The bore 18a extends perpendicular to the document 1. Each slug has attached thereto a leaf spring 20 which is connected to the slug carrier by projecting through a slot in one of the interposers. The leaf spring 20 maintains the slug's flange 16a in contact with the open end of its asociated interposer and returns the slug after it has been driven toward the document.

As illustrated in FIG. 3, the print chain 3 also comprises a flexible toothed endless belt 21 whose teeth 22 mesh with peripheral notches (not shown) in pulleys a and 5b. Each slug carrier contains a pair of flanges 23 which project across the edges of the belt 21 and cooperate with pins 24 to secure the slug carrier to the belt. The pins 24 project through holes in the flanges 23 and bores in selected teeth 22 on the belt. The pulleys, 5a and 5b, project between the flanges 23 on the carriers 15 to drivingly engage the belt.

As also illustrated in FIG. 3, each hammer 9 rotates in an arc about a pivot 9!) when activated by energization of an electromagnet 90 to force its striking surface 9d against an interposer 18. As shown, each hammer is T-shaped in cross section with its flange being adapted to strike the interposers. A spring (not shown) is used to return the hammer to its unactivated position. A stop plate 25 is secured to the bottom guide member 8 to inhibit the print chain from moving toward the document when the interposers are struck by the hammers.

Referring to FIGS. 2 and 3, the operation of the printer is as follows. When it is desired to print a particular type character 17, a selected hammer is activated to drive the slug 16 on which the type character is mounted against the ribbon l3 and document 1. The selected hammer strikes the interposer 18 which is associated with the selected slug and, since the open end of the interposer is in contact with the flange 16b of the slug, the force of the hammer is transmitted to the slug, driving it along the interposers bore 18a and perpendicular to the document. The resilient-mounting member 19 of the interposer confines the impact force from the hammer to the particular interposer-slug combination which is struck. Without the resilient member, hammer impact would cause those slugs adjacent to the one associated with the struck interposer to be driven toward the document. The hammer need not strike the interposer squarely since the slug moves perpendicular to the document along the interposers bore. Neither the angle at which the hammer moves nor the configuration of the striking surface of the hammer affects the slugs direction of move ment. In addition, since the hammer is striking the interposer and not the slug, the hammers need be timed only to strike enough of the interposer to drive the slug toward the document.

Preferably, the hammer strikes the interposer at the harnmers center of percussion. Also, preferably, the mass of each hammer is approximately equal to the mass of each slug so that the hammers stop upon their impact with the interposers. Such a relationship prevents the hammers from interfering with the moving print chain without the necessity of hammer stops. To achieve this approximate equality the hammers illustrated in the drawing are T-shaped in cross section to minimize their mass. ln addition, with the mass of the hammer and the mass of the slug being approximately equal, the interposer is displaced very little, if at all, by the force of the hammer and vibration within the print chain is avoided.

Although in the preferred embodiment disclosed, the slug is guided in its movement toward the document by being located within the bore 18a of the interposer, such external guidance is not necessary in practicing the invention. Without external guidance, the direction of travel of the slug is approximately along a line joining the centroids of the interposer and slug since the slug is maintained in contact with the interposer prior to being driven by the hammer. The direction from which the hammer impacts the interposer has no bearing on the direction of the slugs travel. Even without external guidance of the slug, the direction of hammer movement and the shape of the hammer's striking surface cannot cause the slugs direction of travel to significantly deviate from being perpendicular to the document if the centroids of the slug and interposers are aligned in this direction.

Thus, preferably, in the embodiment disclosed in FIGS. 2 and 3, the interposers 18 are square in cross section and their bores 1911 are also square and centrally located. Both the straight sections and the flanges 16b of the slugs are preferably square with each flange being symmetrically located on its attached straight portion. This arrangement locates the centroids of associated interposers and slugs on a line perpendicular to the document and in the center of the bore. Along with the guidance provided by the bores, the centroid alignment causes the slugs to move perpendicular to the document in response to hammer impact.

We claim:

1. A printer comprising:

a. at least one selectively activatable hammer;

b. a member moving with respect to the document being printed upon;

c. a plurality of print slugs mounted in the moving member, each slug being movable toward the document and having a type character thereon facing the document; and

d. a plurality of interposers mounted in the moving member, each interposer being associated with one of the slugs, adapted to be struck by the hammer and located between the hammer and its associated slug such that at least some of the force of the hammer upon the interposer is transmitted to the slug to drive its type character toward the document.

2. The printer as recited in claim l and including a plurality of resilient members for mounting the interposers in the moving member.

3. The printer as recited in claim 1 and including biasing means for returning each driven slug after it has been driven toward the document.

4. The printer as recited in claim I wherein the mass of the hammer and the mass of each slug are approximately equal.

5. The printer as recited in claim l wherein the hammer is adapted to rotate when activated to strike an interposer.

6. The printer as recited in claim 1 including biasing means for maintaining contact between each pair of associated interposers and slugs.

7. The printer as recited in claim 1 wherein the moving member comprises an endless moving chain adapted to move across the document at the print line and moving in a plane substantially parallel to the document.

8. A printer comprising:

a. at least one selectively activatable hammer;

b. a member moving with respect to the document being printed upon;

c. a plurality of print slugs mounted in the moving member, each slug being movable toward the document and having a type character thereon facing the document;

d. a plurality of interposers mounted in the moving member, each interposer being associated with one of the slugs and the centroids of each pair of associated interposers and slugs being aligned essentially perpendicular to the document, each interposer being adapted to be struck by the hammer and located between the hammer and its associated slug such that at least some of the force of the hammer upon the interposer is transmitted to the slug to drive its type character toward the document; and

e. biasing means for maintaining contact between each pair of associated interposers and slugs.

9. The printer as recited in claim 8 and including a plurality of resilient members for mounting the interposers in the moving member.

10. A printer comprising:

a. at least one selectively activatable hammer;

b. a member moving with respect to the document being printed upon;

c. a plurality of print slugs mounted in the moving member, each slug being movable toward the document and having a type character therein facing the document;

d. a plurality of interposers mounted in the moving member, each interposer being associated with one of the slugs and containing an open ended bore within which a portion of its associated slug is located, the bore being aligned essen-' tially perpendicular to the document, each interposer being adapted to be struck by the hammer and located between the hammer and its associated slug such that at least some of the force of the hammer upon the interposer is transmitted to the slug to drive its type character toward the document. 

1. A printer comprising: a. at least one selectively activatable hammer; b. a member moving with respect to the document being printed upon; c. a plurality of print slugs mounted in the moving member, each slug being movable toward the document and having a type character thereon facing the document; and d. a plurality of interposers mounted in the moving member, each interposer being associated with one of the slugs, adapted to be struck by the hammer and located between the hammer and its associated slug such that at least some of the force of the hammer upon the interposer is transmitted to the slug to drive its type character toward the document.
 2. The printer as recited in claim 1 and including a plurality of resilient members for mounting the interposers in the moving member.
 3. The printer as recited in claim 1 and including biasing means for returning each driven slug after it has been driven toward the document.
 4. The printer as recited in claim 1 wherein the mass of the hammer and the mass of each slug are approximately equal.
 5. The printer as recited in claim 1 wherein the hammer is adapted to rotate when activated to strike an interposer.
 6. The printer as recited in claim 1 including biasing means for maintaining contact between each pair of associated interposers and slugs.
 7. The printer as recited in claim 1 wherein the moving member comprises an endless moving chain adapted to move across the document at the print line and moving in a plane substantially parallel to the document.
 8. A printer comprising: a. at least one selectively activatable hammer; b. a member moving with respect to the document being printed upon; c. a plurality of print slugs mounted in the moving member, each slug being movable toward the document and having a type character thereon facing the document; d. a plurality of interposers mounted in the moving member, each interposer being associated with one of the slugs and the centroids of each pair of associated interposers and slugs being aligned essentially perpendicular to the document, each interposer being adapted to be struck by the hammer and located between the hammer and its associated slug such that at least some of the force of the hammer upon the interposer is transmitted to the slug to drive its type character toward the document; and e. biasing means for maintaining contact between each pair of associated interposers and slugs.
 9. The printer as recited in claim 8 and including a plurality of resilient members for mounting the interposers in the moving member.
 10. A printer comprising: a. at least one selectively activatable hammer; b. a member moving with respect to the document being printed upon; c. a plurality of print slugs mounted in the moving member, each slug being movable toward the document and having a type character therein facing the document; d. a plurality of interposers mounted in the moving member, each interposer being associated with one of the slugs and containing an open ended bore within which a portion of its associated slug is located, the bore being aligned essentially perpendicular to the document, each interposer being adapted to be struck by the hammer and located between the hammer and its associated slug such that at least some of the force of the hammer upon the interposer is transmitted to the slug to drive its type character toward the document.
 11. The printer as recited in claim 10 wherein each slug comprises a straight portion having a flanged end on which its type character is located, the straight portion being contained within the open ended bore of its associated interposer and including biasing means for maintaining the open end of the interposer in contact with the flange of the slug. 